Re: [ATM] How to grind and polish Slumped Mirror

[vorblesnak@peak.org]

> Does this work any better than just mixing glass into the concrete?
>
> Dominic-Luc Webb
>

As far as grinding, there is not much difference.  Grits and tools pretty
much just do their thing regardless of how the glass is attached.  If I
attach the glass to the surface of the tool the channels that are formed
between the pieces of glass allow air into the grind space which fights
suction in the fine wets.  Those same channels seem to allow the mud to
escape so I can grind longer.  On the down side, when first starting out
the channels will suck up a lot of unused grit.  But as the surfaces come
together the suction of the water as the glass moves over the tool will
pull that grit back into action.

The main reason I glue the grinding pieces down is that I can resurface
the tool.  A bit of heat and the epoxy bond breaks down.  I can scrape the
tool surface and put on new glass.  Glass cast in the concrete must just
be covered to resurface the tool.

All of that aside, I have made tools both ways.  I don't know where
Mahmood is, but epoxy may be an expensive or non existent option.  Pitch
would work to attach the glass, and of course your suggestion of casting
it into the concrete is also an excellent idea.

How big of a tool are you making?  My next lunacy project is a 42 inch
ultrathin slumped mirror.  I am making full sized tools for that one.  I
think it is wise to add some steel to the mix on large diameters.

David Davis
Toledo, OR 97391




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